Remote sensing-based assessment of land degradation and drought impacts over terrestrial ecosystems in Northeastern Brazil.

The spatio-temporal assessment of water and carbon fluxes in Brazil's Northeast region (NEB) allows for a better understanding of these surface flux patterns in areas with different vegetation physiognomies. The NEB is divided into four biomes: Amazon, Cerrado, Caatinga, and Atlantic Forest. Land degradation is a growing problem, particularly in susceptible areas of the Caatinga biome, such as the seasonally dry tropical forest. Furthermore, this region has experienced climatic impacts, such as severe droughts. Due to increasing human pressure, the Caatinga's natural land cover undergoes drastic changes, making it a region particularly vulnerable to desertification. In this study, the Moderate Resolution Imaging Spectroradiometer (MODIS) estimates of evapotranspiration (ET) and gross primary production (GPP) were validated in two contrasting areas, dense Caatinga and sparse Caatinga, using eddy covariance (EC) data and then investigated their behavior over 21 years (2000-2021) for the NEB. MODIS products explained around 60% of the variations in ET and GPP, showing higher accuracy in dense Caatinga, while areas of sparse Caatinga presented the lowest GPP, indicating that land degradation has reduced the photosynthetic activity of the vegetation in this area. Based on the analysis of ET and GPP over 21 years, we observed a greater dependence of the sparse Caatinga on climate variability, demonstrating a stronger resilience of dense Caatinga to climate effects. In comparison with the other biomes of the NEB region, we found lower rates of ET and GPP in the Caatinga biome, with averages similar to the Sparse Caatinga. In comparison with the other biomes in the NEB region, we found the lowest averages of ET and GPP in the Caatinga biome, similar to values found in the sparse Caatinga. In forest areas, similar to the monitored DC, they allowed the Caatinga to behave closer to the other biomes present in the region.

Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers.

The Brazilian semiarid region presents a physical water scarcity and high seasonal and interannual irregularities of precipitation, known as a region with periodic droughts. This region is mainly covered by the Caatinga biome, recognized as a Seasonally Dry Tropical Forest (SDTF). Soil water availability directly impacts the ecosystem's functioning, characterized by low fertility and sparse vegetation cover during the dry season, making it a fragile ecosystem vulnerable to climatic variations. Additionally, this region has been suffering from several issues due to human activities over the centuries, which has resulted in extensive areas being severely degraded, which aggravates the impacts from climatic variations and the susceptibility to desertification. Thus, studying the soil-plant-atmosphere continuum in this region can help better understand the seasonal and annual behavior of the water and carbon fluxes. This study investigated the dynamics of water and carbon fluxes during four years (2013-2016) by using eddy covariance (EC) measurements within two areas of Caatinga (dense Caatinga (DC) and sparse Caatinga (SC)) that suffered anthropic pressures. The two study areas showed similar behavior in relation to physical parameters (air temperature, incoming radiation, vapor pressure deficit, and relative humidity), except for soil temperature. The SC area presented a surface temperature of 3 °C higher than the DC, related to their vegetation cover differences. The SC area had higher annual evapotranspiration, representing 74% of the precipitation for the DC area and 90% for the SC area. The two areas acted as a carbon sink during the study period, with the SC area showing a lower CO2 absorption capacity. On average, the DC area absorbs 2.5 times more carbon than the SC area, indicating that Caatinga deforestation affects evaporative fluxes, reducing atmospheric carbon fixation and influencing the ability to mitigate the effects of increased greenhouse gas concentrations in the atmosphere.

Seasonal variation of surface radiation and energy balances over two contrasting areas of the seasonally dry tropical forest (Caatinga) in the Brazilian semi-arid.

Arid and semi-arid environments correspond to one-third of the Earth's terrestrial surface. In these environments, precipitation is an essential and limiting element for vegetation growth and ecosystem biomass productivity. The semi-arid region of Brazil comprises around 11.5% of the national territory, where the Caatinga biome originally composed ~ 76% of this area, with water deficit as a prominent feature, annual rainfall lower than 800 mm, temperatures ranging between 25 and 30 °C, and potential evapotranspiration higher than 2000 mm/year. Research on the dynamics of mass and heat fluxes through techniques such as eddy covariance (EC) has contributed to estimate the magnitude and seasonal patterns of turbulent exchanges between ecosystems and the atmosphere. This study was conducted in an area of dense Caatinga (DC) and another of sparse Caatinga (SC) from 2013 to 2014. It was observed that albedo (α) and net radiation (Rn) were higher in the SC compared with DC since the magnitude of incoming shortwave radiation was higher in this area. It was found that most of the Rn is converted to sensible heat flux (H), mainly during the dry period in the SC, about 50% for H and 20% for λE. The energy balance closure showed that the turbulent fluxes (H + λE) were underestimated in comparison to the available energy at the surface (Rn - G). We also observed that this discrepancy was higher in the DC area, corresponding to ~ 30%.

Effects of temperature on the life cycle, expansion, and dispersion of Aedes aegypti (Diptera: Culicidae) in three cities in Paraiba, Brazil.

The mosquito Aedes aegypti is the primary vector of dengue and is common throughout tropical and subtropical regions. Its distribution is modulated by environmental factors, such as temperature. This study aimed to evaluate the influence of temperature on the life cycle and expansion of Ae. aegypti populations in the cities of Campina Grande, João Pessoa, and Patos. Samples of Ae. aegypti were collected in the three cities and raised in the laboratory. We assessed the life cycles of the three Ae. aegypti populations under six constant temperatures (16, 22, 28, 33, 36, and 39°C), selected on the basis of historical temperature tendencies of each city. We also used existing climate data to calculate projected temperature increases for all three areas. Our results suggest that Campina Grande, João Pessoa, and Patos will experience, respectively, maximum temperature increases of 0.030°C/year, 0.069°C/year, and 0.061°C/year, and minimum temperature increases of 0.019°C/year, -0.047°C/year, and -0.086°C/year. These projected increases will result in temperatures favorable to the Ae. aegypti life cycle, causing rapid population growth. Therefore, Ae. aegypti populations are likely to expand in the mesoregions represented by these cities.

Development of a New Mosquito Retention System for the BG-Malaria Trap To Reduce The Damage To Mosquitoes.

The BG-Malaria trap was recently modified from the BioGents BG-Sentinel trap to collect Anopheles species, including Anopheles darlingi. However, the captured mosquitoes often lose their hind legs in the collector bag, making them difficult to identify. To develop a new collector system that is capable of maintaining the integrity of the mosquitoes collected in the BG-Malaria trap, we conducted a study in the municipalities of Belém (Pará State [PA]) and Porto Velho (Rondônia State [RO]), Brazil, using carbon dioxide-baited BG-Malaria traps with 4 different mosquito collector systems: standard, no bag, rigid short, and rigid long. Results indicated significant differences among the numbers of mosquitoes captured in the 4 different collectors (P < 0.05). Additionally, significantly fewer insects (P < 0.05) were damaged using the rigid short and rigid long collectors than by using the standard and no-bag collectors. We observed that the longer the insects remained in the collector, the higher the number of damaged insects; this effect was the greatest in the standard collector. The results of this study indicate that rigid long collectors were the best suited for use in the BG-Malaria trap.